Add checkout to PR banch into e2e tests

Signed-off-by: michal.gubricky <michal.gubricky@dnation.cloud>

playbooks/openstack/e2e.yaml

@@ -23,6 +23,20 @@
   tasks:
     - name: Determine cluster stack directory
       block:
+        - name: |
+            Set facts -
+            Priority is given to the values of git_reference and git_repo over variables collected from the PR.
+            In cases where git_reference and git_repo are undefined, and e2e is not executed on the PR, a fallback mechanism is employed.
+          ansible.builtin.set_fact:
+            git_branch_name: "{{ git_reference | default(pull_request.json.head.ref) | default(git_reference_default) }}"
+            git_repository_url: "{{ git_repo | default(pull_request.json.head.repo.clone_url) | default(git_repo_default) }}"
+        - name: Checkout to PR branch
+          ansible.builtin.git:
+            repo: "{{ git_repository_url }}"
+            clone: false
+            dest: "{{ project_dir }}"
+            version: "{{ git_branch_name }}"
+          when: zuul.change is defined  # execute when the e2e pipeline is initiated on a PR
         - name: Make sure directory structure exists
           ansible.builtin.file:
             path: "{{ item }}"